Fork lock



Dec. 5, 1967 R. D. VARILEK FORK LOCK Filed Aug. 2, '1965 fz fj United States Patent O 3,356,241 FORK LOCK Ronald D. Varilek, Greendale, Wis., assignor to Allis- Chalmers Manufacturing Company, Milwaukee, Wis. Filed Aug. 2, 1965, Ser. No. 476,469 2 Claims. (Cl. 214-731) ABSTRACT OF THE DISCLOSURE A pair of lift forks are provided with downwardly depending lingers for registration with notches in the upper part of the carriage. The brackets mounting the forks to the carriage permit suflcient relative vertical movement to allow disengagement of thel fingers from the notches when the carriage is lowered slightly after the forks are brought to rest on the floor. With the lingers out of the notches, the forks can be conveniently shifted laterally to a different position on the carriage. If the lift truck is equipped with a carriage side shifter, the carriage rather than the forks may be shifted laterally to reposition the forks on the carriage.

This invention relates to means for releasably and selectively locking a fork in a plurality of laterally spaced positions on a lift truck carriage.

Heretofore, considerable attention has been given to fork lock arrangements for lift trucks, particularly releasable latches which may be manually adjusted to a released position to permit the fork to be adjusted to a new lateral position on the carriage. Latch arrangements have not proven satisfactory due to malfunction of the latch. One major cause of malfunction is infiltration of dirt and other foreign material which makes it diflicult to operate the latch. The rusting of the latch components has also caused malfunction of the latch and in numerous instances the latch cannot be operated manually after the truck has been in service only a short period of time. In some instances the latches are removed by the operator or lift truck user so that the forks can be easily shifted laterally relative to the carriage. This has created a safety problem in that some lift truck designs permit the forks to be slipped laterally oif the ends of the carriage rails on which they are mounted.

It is an object of the present invention to provide an improved, reliable lift fork lock permitting the fork to be easily positioned in one of its several positions along the transverse width of the carriage.

It is a further object of this invention to provide an improved releasable fork positioning means wherein the cooperating locking members are fixedly secured to the fork and carriage.

It is a further object of this invention to provide means for shifting a fork relative to a carriage between releasably locked positions which does not necessitate the lift truck operator leaving the operators station to unlock or shift the fork.

These and other objects and advantages of this invention will be apparent to those familiar with the art when the following description is read in conjunction with the drawings in which:

FIG. 1 is a perspective view of a lift truck incorporating this invention;

FIG. 2 is a side View of a carriage and fork with parts broken away to better show the present invention;

FIG. 3 is a section view taken along the line III-III in FIG. 2; and

FIG. 4 is a View similar to FIG. 2 but showing the fork raised to a nonlocking position.

Referring to FIG. 1, my invention is incorporated in a lift truck 11 having a carriage which is side shifted by ricev a power operated side shifter means including a double acting hydraulic motor 13. The carriage 12 is supported on a mast 14 for raising and lowering movement by lift motor 16 and chains 17 in a conventional manner. Manually operated control levers 18, 19 are provided at the operators station 21 for operating control valves, not shown, which in turn control operation of lift motor 16 and side shift motor 13.

Referring also to FIG. 2, the carriage 12 includes a front section 22 having horizontal upper and lower guide rail structures 23, 24 and a rear section 26 reciprocably mounted on the mast 14 and having upper and lower guide rails 27, 28. The front section 22 of the carriage includes upper and lower slides 31, 32 cooperatively engaging guide rails 27, 28 of the rear section 26. Side shifting of the front section 22 relative to the rear section 26 is achieved by securing the cylinder 33 of motor 13 to bracket 34, which is welded to rail structure' 27, and by securing rod 36 of motor 13 to bracket 37 which in turn is Welded to guard structure 38. The guard structure 38 is welded to slide 31.

A pair of lift forks 41, 42 are positioned on guide structures 23, 24 of carriage 12 and their hook portions 43, 44, 4S, 46 are so proportioned as to permit a predetermined amount of relative vertical movement between the forks and the guide rail structures. This amount of vertical movement is designated by the letter e. As illustrated the guide rail structure 23 has an upwardly extending flange 51 having a plurality of recesses 52 adapted to receive cylindrical locking fingers 53, 54 press lit in bores 56, 57 in hook portions 43, 45. Thus the lingers releasably lock the forks 41, 42 in two of the recesses 52 in the upwardly extending portion 51 of rail structure 23 when the forks rest by gravity on the carriage. The fingers 53, 54 extend vertically downwardly into the recesses 52 a distance less than the distance e. Thus when the carriage is lowered to rest on a support, as indicated by ground line 61 in FIG. 4, and the carriage is further lowered the distance e, the forks can be slid along the ground or floor to a new lateral position. The forks for large lift trucks are so heavy that manual sliding by one man to a new position on the carriage is difficult or impossible. By providing a power operated side shifter, as illustrated, the operator, after lowering the carriage to the position Shown in FIG. 4, may shift the carriage structure 22 sideways with the forks remaining at rest on the ground or floor. When the carriage structure 22 has been shifted to a point where the locking fingers 53, 54 are registered with different recesses 52, the side shifting movement is stopped, by manipulation of control lever 19, and the carriage is then raised, by operating control lever 18, to releasably lock the forks in their new position of adjustment. Thus, with a power operated sideshifted carriage the forks can be shifted laterally of the carriage without requiring the operator to leave his operators station 21.

As shown, the parallel at surfaces 66, 67 on rail structure 24 and fork 41, as well as parallel surfaces 68, 69, are distance e apart in the normal position of the forks as shown in FIG. 2, and in FIG. 4 these surfaces are in engagement. It is obvious, of course, that one of these pairs of surfaces could have greater vertical spacing, however, the toes 71, 72 of the hook portions should overlap the flanges 51, 50 of the carriage in a vertical direction, a distance greater than distance e so that the forks cannot be removed from the carriage except by sliding them olf either lateral end. In other words the forks 41, 42 cannot be unhooked by rotating them forwardly about either their top or bottom hooks.

This invention increases lift truck safety by providing a rugged fork lock which the operator or user will not eliminate as has heretofore occurred with malfunctioning latches. Further, this invention eliminates loose parts by 1. In a lift truck the combination comprising: a carriage having parallel upper and lower guide rail structures extending horizontally, said upper rail structure having7 a plurality of upwardly opening recesses spaced at intervals along the horizontal length of said structure,

lift fork having upper and lower hook portions adapted for connection with said rails to permit a predetermined amount of relative vertical movement therebetween, without disengagement of said fork from said rails, and

a rigid locking linger xedly secured on said fork and engageable selectively with said recesses to prevent shifting of said fork along said rail when the fork rests by gravity on said upper rail structure', said finger being moved vertically out of engagement with one of said recesses when said carriage is shifted downwardly relative to said fork said predetermined amount thereby permitting said fork to be shifted sideways along said rails to a new position wherein said linger registers with another recess.

2. The structure set forth in claim 1 and further comprising power operated side shifter means for said carriage thereby permitting said carriage to be side shifted relative to said fork when said fork is supported independently of said carriage and said carriage is displaced vertically downwardly relative to said fork said predetermined amount.

References Cited UNITED STATES PATENTS 2,847,138 8/1958 Backofen et al. 214-730 2,909,299 10/1959 Quayle 214-730 2,950,831 8/1960 Anzons 214-731 2,975,924 3/1961 Kopanski 214-731 3,166,209 1/1965 Haddock 214-730 GERALD M. FORLENZA, Primary Examiner.

R. B. JOHNSON, Assistant Examiner. 

1. IN A LIFT TRUCK THE COMBINATION COMPRISING: A CARRIAGE HAVING PARALLEL UPPER AND LOWER GUIDE RAIL STRUCTURES EXTENDING HORIZONTALLY, SAID UPPER RAIL STRUCTURE HAVING A PLURALITY OF UPWARDLY OPENING RECESSES SPACED AT INTERVALS ALONG THE HORIZONTAL LENGTH OF SAID STRUCTURE, A LIFT FORK HAVING UPPER AND LOWER HOOK PORTIONS ADAPTED FOR CONNECTION WITH SAID RAILS TO PERMIT A PREDETERMINED AMOUNT OF RELATIVE VERTICAL MOVEMENT THEREBETWEEN, WITHOUT DISENGAGEMENT OF SAID FORK FROM SAID RAILS, AND A RIGID LOCKING FINGER FIXEDLY SECURED ON SAID FORK AND ENGAGEABLE SELECTIVELY WITH SAID REESSES TO PREVENT SHIFTING OF SAID FORK ALONG SAID RAIL WHEN THE FORK RESTS BY GRAVITY ON SAID UPPER RAIL STRUCTURE, SAID FINGER BEING MOVED VERTICALLY OUT OF ENGAGEMENT WITH ONE OF SAID RECESSES WHEN SAID CARRIAGE IS SHIFTED DOWNWARDLY RELATIVE TO SAID FORK SAID PREDETERMINED AMOUNT THEREBY PERMITTING SAID FORK TO BE SHIFTED SIDEWAYS ALONG SAID RAILS TO A NEW POSITION WHEREIN SAID FINGER REGISTERS WITH ANOTHER RECESS. 